Rubber plug for a water-proof connector

Abstract: A rubber plug (3) for a water-proof connector has an inner cylinder (11) and an outer cylinder (16). The rubber plug (3) into which an electrical wire (2) inserted and which is inserted into a cylindrical structure (1) of the water-proof connector sealingly closes the gap between the electrical wire (2) and the cylindrical structure (1). The inner cylinder (11) is provided at a portion which is positioned near the opening of the cylindrical structure (1) of the water-proof connector, for sealingly closing a gap between the electrical wire (2) and the inner cylinder (11). And the outer cylinder (16) has an annular groove (14), and is provided outside the inner cylinder (11) at the portion in such a manner that said outer cylinder (16) surrounds said inner cylinder (11) through the annular groove (14) for closing a gap between the inner cylindrical surface of the cylindrical structure (1) and the outer cylinder (16).

Description: Field of the Invention This invention relates to a plug for a water-proof connector which sealingly closes the gap which may be formed between the connector housing and an electrical wire inserted into it. Description of the Prior Art A conventional rubber plug of this type is as shown in FIG. 6. That is, the rubber plug 50 comprises: a cylindrical plug body 51 which is fitted on an electrical wire; a plurality of outer annular lips 52 formed on the outer cylindrical surface of the cylindrical plug body 51; and a plurality of inner annular lips 53 formed on the inner cylindrical surface of the cylindrical plug body 51. The rubber plug 50 is inserted into the cavity 56 of a connector housing 55 from the right in FIG. 6 in such a manner that the outer annular lips 52 are sealingly pressed against the inner cylindrical surface of the connector housing 55 while the inner annular lips 53 are also sealingly pressed against the outer cylindrical surface of the electrical wire 54. However, the above-described conventional rubber plug suffers from the following difficulty: When, as shown in FIG. 7, a force acts on the electrical wire 54 at the end of the cavity 56; i.e., at the opening of the connector housing 55, to bend the electrical wire 54 laterally of the latter 55 depending on the wiring arrangement, the wall of the rubber plug 50 is compressed by the electrical wire 54 on the side to which the latter 54 is bent, thus forming a gap between the inner cylindrical surface of the cavity 56 and the rubber plug 50, and a gap between the electrical wire 54 and the rubber plug 50. As a result, the connector is no longer water-proof; that is, water may enter the cavity 56. WO-A-86/06883 discloses a water-proof connector construction having a cylindrical housing structure into which an electrical conductor is inserted. An elastomeric plug serves for sealing the cylindrical space between the bore of the housing structure and the connector. This plug is provided with an annular groove in a plug section located fully inside the cylindrical housing structure so that the opening of the cylindrical housing structure, at the region of entrance of the electrical conductor, is continuously closed by the plug. Thus, the ground of the groove just mentioned is located near the opening of the cylindrical structure and the groove extends axially in direction to the inner of the cylindrical housing structure. It is an object of the present invention to provide a plug for a water-proof connector of the kind comprising the features defined in claim 1 and having a good water-tightness even when a bending force is applied to the electrical wire of the connector construction. This object, in accordance with the present invention, is achieved by the features of claim 1. Advantageous embodiments are subject matter of claims 2 and 3. The rubber plug into which an electrical wire is inserted and which is inserted into a cylinder of the water-proof connector sealingly closes the gap between the electrical wire and the cylinder. The inner sleeve is provided at a portion which is positioned near the opening of the cylinder of the water-proof connector, for sealingly closing a gap between the electrical wire and said inner sleeve, and the outer sleeve is provided outside the inner sleeve at the portion in such a manner that said outer sleeve surrounds said inner sleeve with said annular groove therebetween for closing a gap between the inner cylindrical sleeve of the cylinder and said outer sleeve. In the rubber plug according to the present invention, the inner sleeve and the outer sleeve are separated from each other by the annular groove. Therefore, even when the electrical wire is bent to one side, the bending force is scarcely transmitted to the outer sleeve. Hence, the outer sleeve is scarcely compressed on the one side to which the electrical wire is bent, and a gap is scarcely formed between the inner cylindrical surface of the cylinder and the outer sleeve on the other side which is opposite to the firstly mentioned one side to which the electrical wire is bent. Thus, the cylinder into which the electrical wire has been inserted is held water-tight with the rubber plug of the invention. The rubber plug of the invention is advantageous as follows: As was described above, the bending force applied to the electrical wire is scarcely transmitted to the outer sleeve, so that the inside of the cylinder is held water-tight by the outer sleeve sealingly engaged with the latter. Thus, the water-proof connector with the rubber plug of the invention is high in water-tightness. Thus, with the the rubber plug simple in structure according to the invention, the water-proof connector can be maintained high in water-tightness at all times. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing a rubber plug according to a first embodiment of this invention; FIG. 2 is a sectional view showing another rubber plug according to a second embodiment of this invention; FIG. 3 is a sectional view showing another rubber plug according to a third embodiment of this invention; FIG. 4 is a sectional view showing another rubber plug according to a fourth embodiment of this invention; FIG. 5 is a side view form the back end surface of the rubber plug according to the fourth embodiment; and FIGS. 6 and 7 are sectional views for a description of a conventional rubber plug for a water-proof connector. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of this invention will be described with reference to the accompanying drawings. First Embodiment An example of a rubber plug for a water-proof connector, which constitutes a first embodiment of the invention, will be described with reference to FIG. 1. FIG. 1 shows the end portion of a connector housing through which an electrical wire is inserted into the connector housing. In other words, FIG. 1 shows the internal structure of a seal cylinder 1 provided for an electrical wire. A plurality of seal cylinders 1 are arranged side by side, which are communicated with cavities, respectively, which are coaxial with the seal cylinders. An electrical wire 2 with a metal terminal (not shown) fixedly fastened to its top end portion is inserted into each of the seal cylinders 1. A water-proofing rubber plug 3 is mounted on the electrical wire 2 behind the metal terminal. The rubber plug 3 includes an end portion 5 which is compressed by crimping the metal terminal, so that the rubber plug 3 is fixedly mounted on the electrical wire 2. The water-proofing rubber plug 3 will be described in more detail. The rubber plug 3 is substantially in the form of a hollow cylinder made of elastic synthetic rubber. The electrical wire 2 can be inserted into the hollow 4 of the rubber plug 3 in such a manner that it is substantially in close contact with the inner cylindrical surface thereof. Two outer lips 6 are formed on the outer cylindrical surface of the middle of the rubber plug in such a manner that they are spaced axially from each other. Each of the outer lips 6 is in the form of a ring protruded from the outer cylindrical surface of the rubber plug 3, and its outer peripheral portion is substantially round in section when not compressed, and its outside diameter is slightly larger than the inside diameter of the seal cylinder 1. Hence, when the rubber plug 3 is inserted into the seal cylinder 1, the outer peripheral portion is pressed against the inner cylindrical surface of the seal cylinder 1. The outer lips 6 are lower in height and smaller in width towards the depth of the seal cylinder 1 so that the rubber plug can be inserted into the latter 1 with ease (not shown in detail in FIG. 1). Inner lips 7 are formed on the inner cylindrical surface of the rubber plug 3. Each of the inner lips is in the form of a ring protruded from the inner cylindrical surface of the rubber plug 3, and its inside diameter is smaller than the outside diameter of the electrical wire 2, so that the outer peripheral portion of the inner lip is pressed against the outer cylindrical surface (the insulating cover) of the electrical wire 2 when the latter 2 is inserted into the rubber plug 3. The length of the water-proofing rubber plug 3 is so determined that, when the rubber plug 3 is engaged with the connector housing, its rear end portion (on the right side in FIG. 1) is exposed outside the seal cylinder 1. The rear end portion of the rubber plug 3 is shaped as follows: That is, it is extended rearward from the position which is slightly set back from the edge 1a of the opening of the seal cylinder while its diameter is gradually larger towards the rear end, and an annular groove 14 is formed in the rear end face of the rear end portion of the rubber plug 3 in such a manner that it is coaxial with the latter 3, it continues in the circumferential direction and it is smaller in width towards its bottom. The formation of the annular groove 14 divides the rear end portion of the rubber plug 3 into an inner cylinder 11 and an outer cylinder 16. In other words, the annular groove 14 is provided between the inner and outer cylinders 11 and 16, so that an external force applied to one of the inner and outer cylinders is scarcely transmitted to the other. The outside diameter (R2) of the rear end of the outer cylinder 16 is much larger than the inside diameter (R1) of the seal cylinder 1. Hence, when the rubber plug is inserted into the seal cylinder 1 as much as required, the outer cylinder 16 is pressed against the edge 1a of the opening of the seal cylinder 1. The inner cylinder 11 is extended rearward substantially to the same position as the outer cylinder 16, and the former 11 is smaller in wall thickness than the latter 16 so that it suitably follows the deflection of the electrical wire 2. In addition, the inner cylinder 11 has an inner lip 12 along the opening at the rear end. The inner lip 12 is sealingly brought into close contact with the electrical wire 2. When the electrical wire 2 with the water-proofing rubber plug 3 and the metal terminal (not shown) is inserted into the cavity of the connector housing, the positional relationships between the water-proofing rubber plug 3 and the seal cylinder 1 are as shown in FIG. 1. That is, the water-proofing rubber plug 3 is positioned inside the seal cylinder 1, and the outer lips 6 are held pressed against the inner cylindrical surface of the seal cylinder 1 while the inner lips 7 against the outer cylindrical surface of the electrical wire 2. In this case, when the outer cylinder 6 is halfway inserted into the seal cylinder 1, it is deformed inwardly; i.e., towards the annular groove, thus being pressed against the edge 1a of the opening of the seal cylinder 1. The rear end portions of the inner and outer cylinders 11 and 16 are protruded from the opening of the seal cylinder 1, thus being exposed outside. In the case where the electrical wire 2 is bent near the edge 1a of the opening of the seal cylinder 1, the inner cylinder 11 deforms following the electrical wire 2 thus bent; that is, it is kept in close contact with the latter 2. In this case, because of the presence of the annular groove 14 the bending of the inner cylinder 11 scarcely affects the outer cylinder 16. That is, the bending force is scarcely applied to the wall of the outer cylinder 11 on the side to which the inner cylinder 16 is bent; that is, the wall of the outer cylinder 11 on the side is scarcely compressed. Hence, the wall of the outer cylinder 16 on the opposite side will never leave the edge 1a of the opening of the seal cylinder 1; that is, it is kept pressed against it as required. Thus, the outer cylinder 16 is kept pressed against the edge 1a of the opening being fully in close contact with the latter. Therefore, even when a bending force acts on the electrical wire 2, a gap is scarcely formed between the outer cylinder 16 and the edge 1a of the opening of the seal cylinder. In addition, the inner cylinder 16 is held water-tight on the electrical wire 2 by means of the inner lips 12, so that the seal cylinder is maintained high in water-tightness. If the electrical wire 2 is bent through a large angle, then the inner cylinder 11 may have a gap on the side which is opposite to the side to which the electrical wire has been bent. However, the embodiment is practically free from this difficulty, because the inner cylinder 11 is protruded backwardly of the seal cylinder 1 to a predetermined length so that its sealing portion is sufficiently long. Second Embodiment In the above-described first embodiment, the outer cylinder 16 is protruded outside from the edge 1a of the opening of the seal cylinder 1. The outer cylinder 16 may be modified into one 16a as shown in FIG. 2, which constitutes a second embodiment of the invention. That is, in the second embodiment, the outer end face of the outer cylinder 16a is flushed with the edge 1a of the opening of the seal cylinder 1. In this case, the annular groove 14a is formed to a depth that a force acting on the inner cylinder 11 is scarcely transmitted to the outer cylinder 16, and the outer cylinder 16a is so formed that its outer cylindrical surface is suitably pressed against the inner cylindrical surface of the seal cylinder 1. Third Embodiment Furthermore, the outer cylinder may be modified into one 16b as shown in FIG. 3, which constitutes a third embodiment of the invention. That is, the outer cylinder 16b is folded, like an umbrella, over the outer cylindrical surface of the seal cylinder 1. In the third embodiment too, an annular groove 14b is formed between the outer cylinder 16b and the inner cylinder 11 so that the force applied to the inner cylinder 11 by the electrical wire 2 is scarcely transmitted to the outer cylinder 11. Fourth Embodiment FIGS. 4 and 5 show a rubber plug according to a fourth embodiment of the present invention. The rubber plug, which has a taper surface abutted against the edge 21a of an opening of a seal cylinder 30 the similar with the fourth embodiment, is modified in following features: The rear end face of the rubber plug 30 has an annular groove 31. More specifically, the annular groove 31 comprises three divisional grooves 31a as shown in FIG. 5. The annular groove 31 is arranged coaxially with the seal cylinder 30. The divisional grooves 31a of the annular groove 31 are arranged on a circumference and at the equivalent angular interval. Each of the divisional grooves 31a is formed such that the width of the divisional groove 31a equals till the bottom. Under the constitution described above, the inner area divided by the divisional grooves 31a serves as an inner cylinder 32 and the outer area divided by the divisional grooves 31a serves as an outer cylinder 33. The inner cylinder 32 of the fourth embodiment is restrained in part by the outer cylinder through connecting pieces formed between the divisional grooves 31a in contrast to the first embodiment. Therefore, the strength of the inner cylinder 32 increases and the deformation thereof is suppressed in contrast to the first embodiment, in which the annular groove continues along the whole circumference. According to the fourth embodiment, when the electrical wire is bent laterally, the outer cylinder 33 receives little influence thereby and sealing is kept by the taper surface 26 because the inner cylinder 32 and the outer cylinder 33 is almost divided from each other. Furthermore, when the electrical wire 2 is inserted into a hollow 4, the undesirable deformation of the inner cylinder 32 is suppressed because the strength of the inner cylinder 32 increases, therefore the inserting operation can be smoothly performed. The number of divisional grooves may be suitably determined, it is no limited thereby nor thereto.

Claims: A rubber plug for making a water-proof connection between a cylinder and an electrical wire (2), whereby said plug is elongate and in use sealingly closes the gap between the electrical wire which passes therethrough and the cylinder, said plug comprising adjacent a rear end portion thereof an inner substantially cylindrical sleeve (11), an outer sleeve (16, 16a, 16b) extending from an intermediate portion of the plug towards a rear end thereof, and an annular or part-annular groove (14, 14a, 14b, 31a) therebetween, so that if a bending force is applied to the wire it is not substantially transmitted to the outer sleeve, wherein said plug (3) is insertable into said cylinder with its front end leading so that a mid portion of the plug presses against the inner surface of the cylinder and the outer sleeve presses against a rear end portion of the cylinder. Plug according to claim 1, wherein said outer sleeve has an outer taper surface (26) which increases gradually in diameter in the rearward direction, said said taper surface (26) being pressed against the edge (1a) of the opening of the cylinder (1). Plug according to claim 1 or 2, wherein said part-annular groove comprises a plurality of divisional grooves (31a).

Inventors: AOYAMA MASAHIKO, HAYASHI HIROYUKI, SAIJO EIJI, WAKATA SHIGEKAZU, AOYAMA, MASAHIKO, HAYASHI, HIROYUKI, SAIJO, EIJI, WAKATA, SHIGEKAZU, AOYAMA, MASAHIKO, C/O SUMITOMO, HAYASHI, HIROYUKI, C/O SUMITOMO, SAIJO, EIJI, C/O SUMITOMO, WAKATA, SHIGEKAZU, C/O SUMITOMO
Applicants: SUMITOMO WIRING SYSTEMS, SUMITOMO WIRING SYSTEMS, LTD.
Application year: 1994
Main classification: H01R13
IPC codes: H01R13